It doesn’t take an ace detective to figure out the cinematic inspiration for The Happytime Murders. In fact, the film was undoubtedly pitched at one time or another as “Who Framed Roger Rabbit? with puppets.” But there’s one major difference between the two movies. While Robert Zemeckis’ classic offered a brilliantly original melding of animation and live action with a script that respected and then tweaked the conventions of each format, The Happytime Murders isn’t nearly as original. In fact, director Brian Henson and the members of his family have been doing the exact same thing (and doing it better) for 40 years.

Henson is the son of Jim Henson, creator of the Muppets, and the younger Henson has been involved in Muppet production his entire life. Over the years, the Muppets have been featured in numerous TV series and movies, all of which were based on the premise that puppets and people interacted as equals. So, it comes as no surprise to see the exact same thing happen in Happytime Murders. The only difference is that Kermit, Miss Piggy, Fozzie Bear and the rest of the Muppets have built up unique memorable personalities over the years so that turning Kermit into a private eye or Piggy into a femme fatale is quite easy; By contrast, the puppets in Happytime Murders seem like rejected Muppet concepts.

To distinguish Happytime Murders from the various Muppet productions over the years, Henson and screenwriter Todd Berger find a different inspiration, the recent R-rated animated comedy, Sausage Party, and boldly go where no Muppet has gone before, a noirish environment filled with sex, gore (of the having the stuffings blown out of a dead puppet variety), and an almost endless stream of F-bombs and other four-letter words. Unfortunately, while puppets cussing up a storm works in a two-minute red band trailer, it runs out of gas long before Happytime’s 91-minute running time chugs to a halt.

The plot of Happytime Murders is standard 40’s private eye stuff. Puppet detective Phil Phillips (voiced by Bill Barretta), formerly the first puppet detective in the LAPD, starts investigating a series of murders in which someone is killing off the cast of a popular 90’s children’s TV series called “The Happytime Gang.” One of the deceased cast members was Phil’s brother, giving him the requisite personal stake in solving the case. He also has the requisite foil in the Police Department, in this case detective Connie Edwards (Melissa McCarthy), who used to be Phil’s partner on the force before he accidentally shot her during a hostage situation. And he also has the classic old flame, Jenny Peterson (Elizabeth Banks), a stripper who was the only human member of the “Happytime Gang” cast, a new flame, his extremely libidinous puppet client Sandra White, and his would-be flame, faithful secretary Bubbles (Maya Rudolph), who holds an enormous candle for Phil.

There’s plenty more plot in Happytime Murders in case anyone is interested, which I somehow doubt, because none of these detective tropes and clichés, singly or in combination, make for an entertaining storyline, and, with the exception of Maya Rudolph, none of the human actors are really able to exploit the comic potential of their roles. Rudolph is hilarious in every scene as the dim-bulb blonde secretary. She knows how to exaggerate the character to make it funny regardless of whether she is playing off humans or puppets.

Unfortunately, she seems to be the only actor who gets how a film like this should work. The rest of the cast appear lost, waiting for the next puppet joke to possibly garner some laughs. To be fair, a lot of the puppet jokes do work, only not the ones you might think. The premise of puppets cussing and having sex wears thin very quickly (a ridiculously stretched-out sex scene between Phil and Sandra is by far the lowlight of the film), but Henson has decades of experience working with puppets like these, and he knows what is inherently funny. So, we get scenes that mock the often ridiculous appearance of the puppets and their physical attributes (a frightened rabbit lays a couple of Easter eggs), and jokes about puppet construction work well, too (one character is murdered by turning loose some adorable puppies who use the unfortunate victim as a chew toy).

The ratio between jokes that work and those that don’t, however, isn’t high enough to rescue Happytime Murders, because too many of the jokes that don’t work are astonishingly, jaw-droppingly bad. Further, even in the scenes that do work, audiences are often thinking how much better they would have been with Kermit and Miss Piggie rather than the B-list of leftover puppets here. Indeed, a Muppet Maltese Falcon might well have been hilarious.

One thing that Henson and his team do well are the special effects. The Happytime Murders is one movie for which it pays for audiences to stay through the closing credits to see outtakes demonstrating how some of the puppet scenes were done. The audience can marvel at the cleverness revealed in the outtakes, while the bulk of the film is seamless interplay between people and puppets.

The Happytime Murders boasts a competent human cast, good vocal work (many of these actors have voiced some of the Muppets), and great puppet work. What it doesn’t boast, however, is a clever, original script, and most of its failings come down to an overreliance on a concept that wears thin very quickly and an inability to satirize a genre that was skewered so much better 30 years ago in Who Framed Roger Rabbit? Indeed, Henson and his team should have taken notes from the Zemeckis film and the Muppets’ own history to come up with a pointed yet funny film instead of this miss-and-hit effort. In the end, there just aren’t enough happy times in The Happytime Murders.

In this scene, Melissa McCarthy finds a new way to get high (R-rated language).